Why Might a Low-Pass Filter Cause Distortion in a 600Hz Waveform?

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Discussion Overview

The discussion revolves around the potential distortion of a 600Hz waveform when it passes through a low-pass filter with a passband of 3.5kHz. Participants explore the reasons for distortion despite the frequency being below the filter's cutoff, considering various waveform characteristics and interpretations.

Discussion Character

  • Homework-related
  • Conceptual clarification
  • Debate/contested

Main Points Raised

  • Some participants suggest that the waveform's frequency being below the passband should not cause distortion, questioning the assumptions about distortion in this context.
  • Others inquire about the parameters used to express sinusoidal waveforms, such as amplitude, angular frequency, and phase, indicating a need for clarity on these concepts.
  • A participant prompts a broader interpretation of "distortion," suggesting that different forms of distortion should be considered in the analysis.
  • There are requests for the transfer function of a low-pass filter and its implications on output amplitude and phase for a 600Hz input, indicating an interest in the mathematical modeling of the situation.
  • One participant asks for clarification on the shape of the voltage waveform, hinting that the waveform's characteristics may influence the distortion experienced.

Areas of Agreement / Disagreement

Participants do not reach a consensus on the reasons for potential distortion. There are multiple competing views regarding the interpretation of distortion and the characteristics of the waveform.

Contextual Notes

Limitations include the lack of clarity on the specific waveform shape and the assumptions made about distortion in relation to the filter's characteristics. The discussion does not resolve these uncertainties.

Who May Find This Useful

Students and practitioners interested in signal processing, filter design, and waveform analysis may find this discussion relevant.

fran1942
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Homework Statement



We have a waveform with peak to peak amplitude 2V and a frequency of 600Hz. If this signal is to pass through a low-pass filter with a passband of 3.5kHz, explain why some distortion may occur to the waveform when shown on an oscilloscope.


The Attempt at a Solution



I thought there would be no distortion because the wave frequency is well below the passband of 3.5kHz.
Can someone please give me some ideas as to why some distortion may occur. Or at least point me in the right direction.
Thanks kindly for any help.
 
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fran1942 said:

Homework Statement



We have a waveform with peak to peak amplitude 2V and a frequency of 600Hz. If this signal is to pass through a low-pass filter with a passband of 3.5kHz, explain why some distortion may occur to the waveform when shown on an oscilloscope.


The Attempt at a Solution



I thought there would be no distortion because the wave frequency is well below the passband of 3.5kHz.
Can someone please give me some ideas as to why some distortion may occur. Or at least point me in the right direction.
Thanks kindly for any help.
What parameters are used to express sinusoid?
 
amplitude, angular frequency and phase ?

Sorry, I am pretty dense !
I still don't see how some distortion would occur in the case I stated.

Thanks for your persistence.
 
fran1942 said:
amplitude, angular frequency and phase ?

Sorry, I am pretty dense !
I still don't see how some distortion would occur in the case I stated.

Thanks for your persistence.

Can you write the transfer function for a low pass filter with a suitable cutoff frequency?
For a 600Hz input, what's the output amplitude and phase?
 
fran1942 said:
We have a waveform with peak to peak amplitude 2V and a frequency of 600Hz.
Are you meant to interpret this to be a sinewave?
If this signal is to pass through a low-pass filter with a passband of 3.5kHz, explain why some distortion may occur to the waveform when shown on an oscilloscope.
You might need to expand your notion of "distortion" to be able to answer this question.
I thought there would be no distortion because the wave frequency is well below the passband of 3.5kHz.
What forms of "distortion" did you consider here?
 
fran1942 said:

Homework Statement



We have a waveform with peak to peak amplitude 2V and a frequency of 600Hz. If this signal is to pass through a low-pass filter with a passband of 3.5kHz, explain why some distortion may occur to the waveform when shown on an oscilloscope.


The Attempt at a Solution



I thought there would be no distortion because the wave frequency is well below the passband of 3.5kHz.
Can someone please give me some ideas as to why some distortion may occur. Or at least point me in the right direction.
Thanks kindly for any help.

Hint: what is the shape of your voltage? Does it look like a sine wave, triangular, spiky, square ... ?
 

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